Method of enclosing a substrate within a heat-shrinkable sleeve

ABSTRACT

A method of enclosing a substrate within a heat-shrinkable sleeve, which comprises the steps of: 
     a) attaching to the substrate a slideway; 
     b) attaching to the slideway a clip having at least two legs; 
     c) positioning a heat-shrinkable sleeve around the substrate; 
     d) sliding the clip by means of the slideway and with respect to the substrate such that at least one portion of the sleeve becomes positioned between the legs of the clip, and 
     e) causing heat-shrinkage of the sleeve.

The present invention relates to a method of enclosing a substrate,particularly to provide environmental protection, especially byemploying a heat-shrinkable sleeve, and preferably where the substratecomprises a cable or a pipe, particularly a telecommunications cable.

Environmental protection is required around cable splices generally tomake good a cable Jacket that has been removed from the cable ends toexpose the internal conductors for electrical (or optical) splicing. Acable splice case is built up around the cable splice such that itbridges intact cable Jacket at each side of the splice. In this waycontaminants such as moisture can be kept away from the otherwiseexposed conductor splices. Splice cases are now commonly made byinstalling around the splice a dimensionally-recoverable, usuallyheat-shrinkable, sleeve. A heat-shrinkable sleeve may be suppliedover-size, and then heated to cause close, environmentally-sealing,fitting to the underlying cable splice. A wrap-around heat-shrinkablesleeve is disclosed in GB 1155470 (Raychem).

A sleeve may be installed directly over the cable splice or othersubstrate to be protected, or a liner or other article may first beinstalled and the sleeve then shrunk around the liner. Such a liner maygive mechanical strength to the resulting splice case, may protect thesubstrate from the heat applied during heat-shrinkage of the sleeve, ormay add to the water-vapour barrier properties of the sleeve. Where thesubstrate is of non-uniform cross-sectional size (as in the case of acable splice that is of larger diameter at its centre, and tapers downto the diameter of the spliced cables at its ends) the liner may serveto render the changes in size smooth thereby facilitating installationof the sleeve. In order to do this the liner may have frusto-conicalends, which may be produced by providing tapering fingers at the ends ofa cylinder (giving the appearance of crowns) which are then bent inwardstowards the axis of the cylinder. The cylinders may, for example,comprise two half-shells or may result from rolling up an initiallysubstantially flat sheet. Such liners are described in GB 1431167(Raychem).

The ability to communicate with the inside of a splice case may beuseful, for example to monitor or to change conditions therein. Forexample, some telecommunications cables are pressurized with dry air toprotect them, and pressure access points are needed for supply of air orfor testing. In order to do this some line such as a pressure-accesstube must pass through the sleeve, or between the sleeve and thesubstrate enclosed thereby. This has been suggested in, for example, EP0244209 (Raychem) which discloses provision of a valve in the sleeve.Electrical or other communication may be required for other purposes,and GB 2112224 (Raychem) may be cited as a further example.

A different approach is taken in U.S. Pat. No. 4400579 (the disclosureof which is incorporated herein by reference) which relates principallyto sealing a branch-off between two cables using a heat-shrinkablesleeve and a clip between them that forms two conduits in an end of thesleeve. That patent discloses an assembly comprising a heat-shrinkablesleeve capable of being positioned around at least first and secondelongate substrates, and a clip having at least two elongate legscapable of being positioned over the outer surface of the sleeve at anend thereof so as to form, and maintain during subsequent heat-shrinkageof the sleeve, at least two terminal conduits respectively capable ofreceiving the first and second substrates, the clip optionally beingformed as a trident with the central leg of the trident inside thesleeve. The central leg of the trident may be hollow to provide an inletfor pressurized air within a cable splice. That is illustrated in FIG.14, and FIG. 15 shows an alternative where a two-legged clip is usedtogether with a separate inlet that acts as a second separate branchingsubstrate.

The combined clip and valve of FIG. 14 of U.S. Pat. No. 4400579 might,however, be difficult to use under certain conditions, and we have nowdevised a modified technique for forming an enclosure using a clip.

Thus, the present invention provides a method of enclosing a substratewithin a heat-shrinkable sleeve, which comprises the steps of:

(a) attaching to the substrate a slideway;

(b) attaching to the slideway a clip having at least two legs;

(c) positioning a heat-shrinkable sleeve around the substrate;

(d) sliding the clip by means of the slideway and with respect to thesubstrate such that at least one portion of the sleeve becomespositioned between the legs of the clip; and

(e) causing heat-shrinkage of the sleeve.

These method steps may be carried out in any suitable order.

The substrate is preferably elongate, and more preferably comprises apipe or a cable such as a telecommunications cable. In particular, itcomprises a cable splice. Step (a) preferably comprises fixing theslideway against movement along the substrate, and step (a) preferablycomprises sliding the clip along the slideway. When we refer to acomponent (such as the slideway) being fixed, we merely mean fixedagainst the sort of forces that it is likely to encounter. Thus, in theembodiment referred to, sliding of the clip causes the clip to slidewith respect to the slideway which is preferably not displaced byfriction of the sliding clip.

The slideway may comprise first and second parts that movetelescopically with respect to one another, the first part beingattached to the substrate and the second part being attached to theclip.

In another embodiment the substrate is elongate, and the slideway isattached to the substrate to allow movement thereof along the substrate,and the clip is fixed to the slideway against movement along theslideway.

The slideway preferably comprises a tube, preferably a substantiallyrigid tube, preferably comprising metal, and preferably having meanssuch as a valve that can control passage of fluid therethrough.

In some embodiments the slideway is elongate and at least when installedprovides a fixed third leg of the clip, preferably positioned betweenand substantially aligned with said two legs, step (d) resulting in aloop of sleeve passing between said two legs and around the slideway. Inpresently preferred embodiments, however, the slideway is elongate andat least when installed passes through a bridge portion Joining said twolegs of the clip such that the slideway is preferably positionedbetween, is substantially aligned with and is slidable with respect tosaid two legs, step (d) resulting in a loop of sleeve passing betweensaid two legs and around the slideway.

Particularly where the slideway or some other component is intended toprovide fluid communication between the environment and the inside ofthe resulting enclosure, the slideway is preferably positioned such thatit extends from a position that becomes enclosed by the sleeve to aposition that remains outside the sleeve. The seal provided by aheat-shrinkable sleeve is often enhanced by the presence of a coating ofa hot-melt adhesive or other sealing material on an inner surface of thesleeve, which sealing material may flow on heat-installation of thesleeve to fill any voids that would otherwise remain as leak paths. Itis desirable that such sealing material does not block the end of theslideway to be within the final enclosure, and the slideway is thereforepreferably fixed to the cable such that that end remains at the sameposition. The clip is then preferably slid along the slideway to engagethe sleeve.

The sleeve is preferably installed after a liner has been correctlypositioned around the cable splice, and a liner having crowned ends (seeGB 1431167 referred to above) may be located by taping its crowned endsonto the cables. With the crowned ends thus secured it would in generalbe impossible to force a pressure access tube past the crowns into thesplice case volume within, which is where an end of the tube must be ifit is not to become blocked with Sealing material. Thus, such a tubeshould be installed before (or during) installation of the liner, andtherefore before installation of the sleeve. This desirable or essentialsequence of installation steps prevents use of a clip bearing a valvetube (such as that shown in FIG. 14 of U.S. Pat. No. 4400579, referredto above) since the clip must be slid over the sleeve aftersubstantially correct positioning of the sleeve. This problem isovercome by the present invention.

A clip that is attached to the slideway may serve to form a branch-offbetween two substrates that is to be sealed by the sleeve. We presentlyprefer, however, that said clip serves only to locate the slideway andto help seal around it, preferably by causing or facilitatingconformance of the sleeve around it. Where a branched cable splicerequiring pressure access is to be sealed, we prefer that branch-offclips be used that are separate from, and act independently of, the clipplus slideway of the present invention.

The slideway can be fixed with respect to the cable in any suitable way.At present, at least where the slideway comprises an elongate tube, weprefer that at least one and preferably two or more collars be providedaround the slideway. These collars may then be secured to the cable byfor example tapes, bands or hose clamps such those known by the TradeMark "Jubilee Clips"). The collars may have acircumferentially-extending recess for receipt of the band or tape etc.The collars may hold the slideway a small distance (for example 1-5 mm)from the cable so that the clip, through a hole in which the slidewaymay pass, is free to move.

One such collar is preferably positioned at (or inwardly) of theposition to which the ends of the crowns of a liner will reach. Then,and if means is provided on the slideway preventing it being slid out ofthat collar, the end of the slideway will be retained inside the linerand undesired blocking of it by adhesive during installation will beavoided. We prefer that the crown ends meet the collar, and are tapeddown onto it.

An end of the slideway that remains outside the sleeve is preferablyangled away from the cable for ease of connection to an air supply lineor pressure gauge. That end may also be provided with a valve such asthat known by the Trade Mark, "SCHRADER", and optionally with a valvecap.

The slideway and/or the clip may be coated, or otherwise used with, asealing material such as a hot melt adhesive.

The slideway and/or the clip may serve also as electrical communicationto the inside of the sleeve, for example for connection to the shieldlayer of the cable which will in general be exposed at the end of thecable Jacket.

If desired, the legs of the clip may be moveable relative to oneanother, and/or moveable in orientation relative to that of theslideway. Movement together of the legs and locking in thatconfiguration after the clip has been brought to the sleeve mayfacilitate installation.

The sleeve may comprise any suitable material, particularly one based oncross-linked polyolefin and preferably coated with a polyamide or otherhot-melt adhesive. A preferred sleeve comprises a fibre-reinforcedcomposite material, particularly one that is heat-shrinkable by virtueof heat-shrinkable fibres therein. Such a composite material may bereinforced by non-shrinkable fibres, for example glass. The sleeve ispreferably of wraparound design.

The invention is further illustrated with reference to the accompanyingdrawings, in which

FIG. 1 shows a prior art branch-off clip incorporating a valve;

FIG. 2 shows the prior art clip of FIG. 1 in use with a heat-shrunksleeve around a cable;

FIGS. 3-5 show various clip and valve combinations; and

FIG. 6 shows a clip and valve being used according to the invention.

FIG. 1 shows a prior art branch-off clip 51 incorporating a valve asshown in FIG. 14b of U.S. Pat. No. 4400579 (Raychem). The clip is atrident whose central leg 53 is hollow and is provided with a valve 54and an inlet duct 55. The central leg 53 acts as a substrate in thebranch-off technique disclosed in that prior art. The way in which thatbranch-off is made is shown in FIG. 2 (FIG. 14a of U.S. Pat. No.4400579). The clip 51 is simply positioned over the end of a sleeve 52(shown partially) so as to form two conduits in the sleeve, one of whichis occupied by a cable 56 and the other by the central leg 53 of theclip. The hollow central leg 53 therefore provides pressure access intothe enclosure formed by the sleeve (ie into the right hand part of thesleeve, most of which is omitted from the drawing). The sleeve 52 isshown in its shrunk state in which it can be seen tightly to engage thecable 56 and the central leg 53.

FIG. 3 shows a slideway 1 to which a clip 2 is attached such that theclip can slide along the slideway. The clip comprises two legs 3 and abridge portion 4 which may be of any suitable shape and preferablythrough which the slideway passes. The clip may have a hollow middle legaligned with the legs 3 and through which the slideway 1 passes. Thatmiddle leg may be coated with or may comprise a hot-melt adhesive orother sealing material. Collars or other means 5 are provided by meansof which the slideway can be fixed or otherwise attached to a cable orother substrate. The collars 5 may have circumferentially-extendingrecesses or holes 6 therein by means of which the collars may be fixedby bands etc to an underlying cable. The slideway may have an end cap 7or other means, for example of interference fit to prevent completewithdrawal of the slideway through the collar 6. An end of the slidewaythat remains exposed may be shaped as at 8 away from an underlyingsubstrate for ease of access to a valve 9 etc that it may carry.

FIG. 4 is similar to FIG. 3 except that the slideway 1 is intended toslide with respect to a cable on which it is to be mounted. The slidewayslides within a collar 5, and the clip 3 is fixed with respect to, andmay be integral with (at position 10) the slideway 1. A portion of theslideway may be coated or otherwise supplied with a hot-melt adhesive orother sealing material 11. If desired, such a sealing material may besupplied separately in this or other embodiments.

In FIG. 5 the slideway 1 is in (at least) two telescopic parts 12 and 13one of which can slide within (or adjacent) the other. One or each partmay be coated with or comprise a hot-melt adhesive or other sealingmaterial. An electrical connection, such as a lead 14, is provided whichcan allow communication into a splice case which the slideway and cliphelp to form.

Any of the clips used in the invention may be provided with legs thatare fixed or are moveable with respect for example to one another.Moveable legs may facilitate positioning of the clip correctly withrespect to the sleeve. For example, the clip may be slid into positionand the legs then correctly positioned with respect to each other and/orwith respect to the slideway. In a preferred embodiment, each leg ispivotally fixed to a bridge portion of the clip such that the distalends of the legs can swing together to meet the sleeve. A lockingmechanism may be provided to prevent them opening out again in use.

Formation of a splice case is shown in FIG. 6. Here a heat-shrinkablesleeve 15 is positioned around a cable 17, which may be spliced to oneor more other cables within the sleeve, to the right-hand side of thepart of the sleeve illustrated. A liner 16 surrounds the cable andsplice within the sleeve 15, and a crowned end of the liner 18 hastapered fingers thereof bent inwards towards the axis of the liner anddown onto the cable. The fingers may be taped in that configuration tolocate the liner with respect to the cable. The collars 5 are secured tothe cable 17 by bands 19 that pass around the cable and around orthrough the collars 5. The crowns 18 are preferably aligned with andoptionally taped down onto one of the collars 5 and corresponding band19. After the slideway i has been located with respect to the cable 17by means of the collar 5 and bands 19 and the liner 16 and sleeve 15 putin place, the clip 2 is slid in the direction of the arrows over an endof the sleeve, thus deforming the sleeve around the slideway. The sleeveis then shrunk to produce a sealed outlet thereof analogous to thatshown in FIG. 2. The sleeve may be internally coated with a hot-meltadhesive or other sealing material to improve the seal between it andthe underlying cable.

For the avoidance of doubt, it is here noted that the invention providesarticles, methods and kits for enclosing a substrate or providingpressure access or other communication. Any one or more of the clips,slideways, fastening devices, sleeves or liners may be selected.

We claim:
 1. A method of enclosing a substrate within a heat-shrinkablesleeve, which comprises the steps of(a) attaching a slideway to thesubstrate; (b) positioning a heat-shrinkable sleeve around thesubstrate; (c) sliding a clip, having at least two legs being attavchedto the slideway, with respect to the substrate such that at least oneportion of the sleeve becomes positioned between the legs of the clip;and (d) heating the sleeve to cause heat-shrinkage thereof.
 2. A methodaccording to claim 1, in which the substrate comprises an elongatesubstrate, step (a) comprises fixing the slideway against movement alongthe substrate, and step (c) comprises sliding the clip along theslideway.
 3. A method according to claim 1, in which the slidewaycomprises first and second parts that can move telescopically withrespect to one another, the first part being fixed to the substrate andthe second part being fixed to the clip.
 4. A method according to claim1, in which the substrate comprises an elongate substrate and theslideway is attached to the substrate to allow movement thereof alongthe substrate, and the clip is fixed to the slideway against movementalong the slideway.
 5. A method according to claim 1, in which theslideway comprises a tube.
 6. A method according to claim 5, in whichmeans is provided that can control passage of fluid through the tube. 7.A method according to claim 1, in which the slideway is positioned suchthat it extends from a position that becomes enclosed by the sleeve to aposition that remains outside the sleeve, thereby providingcommunication between the inside and outside of an enclosure formed byshrinking the sleeve around the substrate.
 8. A method according toclaim 1 in which the clip has first and second legs substantiallyaligned with each other, and the slideway is elongate and provides athird leg positioned between the substantially aligned with the firstand second legs, and the step of sliding the clip with respect to thesubstrate such that at least one portion of the sleeve becomespositioned between the legs of the clip results in a loop of the sleevefastened between the first and second legs and around the slideway.
 9. Amethod according to claim 1 in which the clip has first and second legssubstantially aligned with each other and joined by a bridge portion,and the slideway is elongated and passes through the bridge portion suchthat the slideway is positioned between and is substantially alignedwith and is slideable with respect to the first and second legs, and thestep of sliding the clip with respect to the substrate such that atleast one portion of the sleeve becomes positioned between the legs ofthe clip results in a loop of sleeve passing between said two legs andaround the slideway.